Proximate, syn-periplanar bisdiazenes/bisdiazeneoxides - syntheses, photochemistry

Cullmann, Oliver; Vögtle, Markus; Stelzer, Frank; Prinzbach, Horst

doi:10.1016/s0040-4039(98)00247-0

Cited by 11 publications

(5 citation statements)

References 14 publications

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“…The bisdiazenes of type K utilized in this study are listed in Figure ; the details of their synthesis have been ( 1 , 2 , 6 , 7 23 ) or will be ( 3 , 4 , 5 ) part of separate publications . The skeletal substitution in 1 , 2 , and 6 was dictated by synthetic reasons, that in 5 was effected in order to enforce a shortening of the π,π distance and to prohibit diazene → hydrazone tautomerization.…”

Section: Substratesmentioning

confidence: 99%

Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations

et al. 2000

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Cyclic delocalization of five and six electrons, respectively, in the plane of four N centers was explored by one-/two-electron reduction of more or less rigid, parallel bisdiazenes (1-7), with NdN/NdN distances (d ππ ) ranging from ∼2.8 to 5.0 Å, interorbital angles (p,p; ω) from ∼l75°to 90°, and with more or less kinetic protection. For the "proximate" substrates 1-5 (d ππ ≈ 2.8-3.2 Å, ω ≈ 175-156°), short contact with alkali metals (Li, Na, K, Cs) generates turquoise to deeply green radical anions (λ max (DME) ≈ 700-900 nm). The character of these radical anions as cyclically in-plane delocalized bishomoconjugated 4N/5e species with a high concentration of spin density between the NdN units is established by extensive UV/vis, electrochemical, and EPR measurements (CW, pulsed) at temperatures down to 8 K, and by DFT calculations (B3LYP/6-31G*). After longer exposure to the metals, the three most persistent 4N/5e radical anions (M + 1 •-, M + 2 •-, M + 5 •-) are further reduced to the red dianions (2M + 1 2-, 2M + 2 2-, 2M + 5 2-, λ max (THF) ≈ 360-430 nm). Of the nine ion pair combinations with Li + , Na + , and K + all except one (2K + 1 2-) are thermally highly persistent. For the dianions the l H, l3 C, and 7 Li NMR analyses assisted by DFT calculations confirm the 4N/6e σ-bishomoaromatic electronic structure. The reduction potentials determined (CV) for dialkyl-diazenes (8-10) and bisdiazenes (1, 2, and 5) allow an estimate of the thermodynamic stabilization of the respective radical anions and of the gain in electron delocalization energy in the dianions (σ-bishomoaromaticity).

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Section: Substratesmentioning

confidence: 99%

Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations

et al. 2000

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“…A third alternative to be considered (route C) involves cyclization to C ssymmetrical oxaziridine 63, [2 π ϩ2 σ ]photocycloaddition (C s -64), and [3ϩ2]cycloreversion. In fact, efficient diazene oxide Ǟ oxadiaziridine cyclizations had been observed in structurally related systems, [9][10][28] [30] and for the subsequent photostep, there are also a number of related examples. [14][31] Scheme 8 For the distinction of the routes A and C, the highly optically enriched (-)-12 had been prepared (Scheme 4).…”

Section: Mechanistic Aspectsmentioning

confidence: 99%

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

et al. 2000

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Of two very proximate syn‐periplanar bisdiazenes (1,2) mono‐, di‐, tri‐ and tetra‐N‐oxides were prepared, representing six combinations of the individual NN/NNO/ONNO chromophores. According to DFT calculations (B3LYP/6‐31G*), [2+2]photocycloaddition to the respective oxidized tetrazetidines is significantly to moderately endothermic. The metathesis isomerization of the oxidized tetrazetidines is generally highly exothermic and kinetically increasingly favorable with increasing oxidation state. In practice, four out of the six bichromophoric combinations undergo selectively, in competition with N2 elimination from a DBH unit (13) still partially, metathesis isomerization upon π → π* excitation (monochromatic 254 nm light). In the case of the syn‐NNO/NNO combinations (5/6, 14), the photoaddition is thermally reversed. For a ONNO/NN combination (30), internal electron transfer is responsible for a complex reaction pattern. The preparative value of the metathesis reactions, though, is limited: The metathesis‐derived bis[diazene mono(di)oxides] undergo relatively fast secondary photoreactions, while the tri(tetra)oxides undergo rapid thermal transformations. For the NN/NNO systems (12), of three potential pathways for its metathesis isomerization, the one that takes place via σ‐symmetric intermediates (63, 64) is excluded by virtue of the retention of optical purity in the photometathesis of a highly enriched enantiomer [(−)‐12]. Matrix irradiation experiments (12 K, IR control) with 12 result in the appearance of a kinetically highly labile transient. Supported by DFT calculations it is concluded that in the metathesis reactions, the respective tetrazetidine oxides (increasingly destabilized by interactions between oxygen lone pairs and NNσ* orbitals) function as vibrationally excited transients. That thermal reversion of these transients might be a general, nonproductive competition, is suggested by the experimental verification of a “reversed photometathesis” (51 → 15) and by the generally low rates in product formation upon irradiation. The question remains to be answered why in structurally analogous molecular skeletons, [2+2]photocycloaddition occurs in the CC/NN and variously oxidized NN/NN, and not, however, in the parent NN/NN combinations.

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“…One year later, Hansen and Wodtke reported the first evidence for the production of a ring isomer of N 3 , which is confirmed by later experimental − and theoretical , work. The synthesis of the N 4 ring was attempted as early as 1982 through a (2 + 2) cycloaddition reaction, − but it was not until 2012 that Camp and co-workers detected a tetraalkyl tetrazetidinetetracarboxylate radical cation, which was the first discovery of a substituted N 4 ring in experiment as far as we know.…”

Section: Introductionmentioning

confidence: 99%

Mass Spectrometry and Theoretical Investigation of VN_n⁺ (n = 8, 9, and 10) Clusters

Ding¹,

Yang

et al. 2018

J. Phys. Chem. A

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VN clusters were generated by laser ablation and analyzed by mass spectrometry. The results showed that VN, VN, and VN clusters were formed, and the mass peak of VN is dominant in the spectrum. The VN cluster was further investigated by a photodissociation experiment with 266 nm photons. Density functional theory calculations were conducted at the M06-2X/6-311+G(d,p) level to search for stable structures of VN ( n = 8, 9, and 10) and their neutral counterparts. The theoretical calculations revealed that the most stable structure of VN is in the form of V(N) with D symmetry. The binding energy from the calculation is in good agreement with that obtained from the photodissociation experiments. The global minimum structures of VN, VN, and VN contain a similar substructure of the N ring and exhibit energy properties. The most stable structure of VN is in the form of (η-N)VN(N) with C symmetry, while that of VN is in the form of (η-N)V(N) with C symmetry. For neutral VN, VN, and VN, (η-N)V(N), (η-N)V(N)(N), and (η-N)V(N) are their ground-state structures, with decomposition into one V atom, and corresponding quantities of N can release energies of about 50.20, 96.28, and 57.76 kcal/mol, respectively.

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Proximate, syn-periplanar bisdiazenes/bisdiazeneoxides - syntheses, photochemistry

Cited by 11 publications

References 14 publications

Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations

Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Mass Spectrometry and Theoretical Investigation of VN_n⁺ (n = 8, 9, and 10) Clusters

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Proximate, syn-periplanar bisdiazenes/bisdiazeneoxides - syntheses, photochemistry

Cited by 11 publications

References 14 publications

Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations

Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Mass Spectrometry and Theoretical Investigation of VNn+ (n = 8, 9, and 10) Clusters

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Mass Spectrometry and Theoretical Investigation of VN_n⁺ (n = 8, 9, and 10) Clusters